Components, such as an engine, a motor, and an exhaust gas recirculatuion (EGR) valve, which are noise sources are housed in an engine compartment. These components have three-dimensional shapes. In order to reduce noise, it is therefore desirable that a sound absorbing material be placed along a plurality of surfaces of each of these components. That is, sound absorbing covers having a three-dimensional shape so as to cover the surroundings of the components are needed.
Foam such as polyurethane foam is often used as a sound absorbing material and a vibration absorbing material. However, foam includes therein a large number of cells (bubbles) and thus has low thermal conductivity. Therefore, placing such foam around the engine, the motor, and other components, which emit heat, can cause malfunction because of accumulation of heat. Therefore, how to improve heat radiation performance of the foam is an issue when foam is used as a sound absorbing material.
Patent Document 1 describes a sound absorbing cover made of foam containing magnetic filler. In the sound absorbing cover described in Patent Document 1, the magnetic filler having high thermal conductivity is oriented in the thickness direction of the sound absorbing cover. This allows heat of a mating member to be promptly released through the oriented magnetic filler.